Patients screened for HDL cholesterol, apo A-I and apo A-II levels. HDL turnover is assessed in vivo to determine synthetic and catabolic rate of HDL apolipoproteins. Nutritional perturbations of HDL metabolism are assessed by studying patients on low and high fat diets. The influence of alcohol on HDL metabolism is also under study. Genetic regulation of HDL metabolism is being assessed by performing HDL turnover studies in twins.